Extracting Contact Effects in Organic FETs

Contact resistances between organic semiconductors and metal electrodes have been shown to play a dominant role in electronic charge injection properties of organic FETs (OFETs). These effects are more prevalent in short channel length devices and therefore should not be ignored when examining intrinsic properties such as the mobility and its dependence on temperature or gate voltage. Here we outline a general procedure to extract contact current-voltage characteristics and the true channel mobility from the transport characteristics in bottom-contact poly (3-hexylthiophene) FETs, for both ohmic and nonlinear charge injection, over a broad range of temperatures and gate voltages. Distinguishing between the contact and channel contributions in bottom-contact OFETs is an important step toward improved understanding and modeling of these devices.